Treatment of iron and steel to prevent corrosion.



wninrm n. ALLEN, or DETROIT, MICHIGAN.

TREATMENT OF IRON AND STEEL TO PREVENT CORROSION.

No Drawing.

To all whomz't may concern:

Be it known that I, WILLIAM H. ALLEN,

a citizen of the United States, and residing at Detroit, in the county of 'Wayne and State of Michigamhave invented a new and Improved Treatment of Iron and Steel to Prevent Corrosion, of which the following is a specification.

This invention relates to the treatment of articles of iron or steel whose surfaces have been treated to change them from metallic iron to phosphates of iron; and its object is a process whereby such portions of the surfaces, which, by reason of improper or-inefiective actions of the compounds of phosphorus employed to produce such surfaces are not rendered non-corrodible under the actions of the elements, may be rendered inactive under such conditions.

When articles of iron orsteel are treated with soluble acid phosphates according to the directions set forth in the patents to Coslett, No. 870,937, dated November 12, 1907, and to Richards, No. 1,069,903, dated .August 12, 1913, for some reason as yet un-' determined, they sometimes rust under water or when exposed to moist air. rusting usually occurs in very small spots or specks and therefore it is possibly due to the formation (segregation) of hydrates of iron, or other compounds capable of cansing rusting occluded in the phosphatic surfaces of themetal articles or formed on such surfaces. I v

In order to render-these undesirable compounds of iron inactive, that is, no longer capable of 'causing rusting, the articles which have been treated with soluble acid phosphates are placed in an approximately The Specification of Letters Patent. Patented Mar, 26,1918, Application filed August 2, 1917. Serial No. 184,041.

five per cent. aqueous solution of ferrocyanid or ferricyanid, preferably ferrocyanid of sodium or potassium, for a short time, after which they are removed, dried and finished in any desired manner.

By this treatment, the small amounts of iron compounds which may cause rusting and which are occluded in the phosphatic surfaces of the articles being treated, are

changed to iron ferro or ferricyanid, 'possibly a mixture of'the two and thereforei nonoorrodible.

1. The method of preventing the rusting of surfaces of articles of iron and} steel which have been changed in part to 'phosphates of iron, which consists in immersing such articles in an aqueous solution i of an iron cyanid of an alkali-metal.

The method of preventing the-rusting of surfaces of articles of iron and steel which have been changed in part'to'phosphates of iron, which consists in immersing such articles in a solution of an iron cyani of potassium. g

3. The method-of preventing the rusting of surfaces of articles of iron and steel which, have been changed in part to phosphates of iron, which consists in immerslng such articles in a solution of ferrocyanid of.

potassium. 7

1. The method of preventing the rusting of surfaces of articles'of iron and steel which have been changed in part to phosphates of iron which consists in immersing such articles in an aqueous solution of a. double cyanid of iron and an alkaline earth n1 eta]. I

WILLIAM H. ALLEN. 

